In response to a social trend toward energy saving and awareness of environmental ecology, electronization has advanced also in the field of automobiles, so that more electronic components are mounted on a periphery of their driving systems, which has led to a growing demand for durability and stability of such electronic components under a high temperature environment. Accordingly, also in the field of inductors, there have been developed products made mainly of a metal material that is a magnetic material having a stable saturation magnetic flux density under a high-temperature environment. Moreover, inductors made of a metal magnetic material are requested to have not only a high-temperature environment capability but also high reliability capabilities such as a moisture resistance capability, a corrosion resistance capability, and so on that are as stable as those of conventional inductors made of a ferrite magnetic material. It is, therefore, also desired that a printing process with respect to such products should not impair these capabilities. Particularly, laser printing, which has recently been used for performing printing on electronic components, has a lot of advantages from the viewpoint of a mass production process. With respect to a metal material, however, the laser printing destroys an insulation coating formed on a metal surface, and thus the use thereof has been avoided.
In printing using laser light with respect to electronic components including those to which a glass coating is applied such as, among others, an inductor (a metal material), as shown in Japanese Patent Application Publication No. Hei 8-31682 (hereinafter “the '682 Publication”), a glass surface and a surface of a matrix thereof itself are ground into a concave state, and light dispersion and a difference in refraction index resulting therefrom are utilized to obtain visibility.
In the technique disclosed in the '682 Publication, a glass surface and a surface of a matrix of an electronic component itself are ground into a concave state, so that a printing portion of a metal core to which a glass coating is applied for the purpose of rust prevention has a decreased glass film thickness. Because of this, intrinsic functions such as, among others, a moisture resistance capability is decreased, leading to a problem that rust becomes likely to be formed. Furthermore, in a case of a metal core to which no glass coating is applied, a thin insulation coating layer formed on a surface of a metal material is destroyed, leading to problems of formation of rust and degradation in insulation capability. Furthermore, in manufacturing, dust originating in glass or a metal material matrix is generated, so that it is required that a process of collecting the dust be newly added, thus making this printing method costly.